Pressure switch



Dec.4 27, 1949 L. J. BORDELON PRESSURE SWITCH Filed March 5, 1948 Snoentor Gttorneg Patented Dec. 27, 1949 PRESSURE SWITCH Lawrence J. Bordelon, San Diego, Calif.,.assig`nox to Consolidated Vulteo Aircraft Corporation, San'Diego, Calif., a corporation of Delaware,

Application March 5, 1948, Serial No. 13,272v

(Cl. 200e-82:)

1 3: Claims. 1

This inventionrelates to devices'for Controlling Lelectrical circuits andmore particularly to cir-A cuit controllingrv devices automatically operable in response torfvariaticns inexternal conditions. An object of-the present invention resides in providing anovel pressure operated mechanism for operating anelectric-switch.automatically in response to variations in Yexternal pressure conditions .to control an electrical-circuit.

Anotherobjectof this invention is tol provide an improvedform of pressure operated electric circuit controllingdevice having a simplicity of construction, `eiliciencyzofI operation and economyr mentor the enginenoselcasing of an aircraftenginev showing thepressureswitch of the pres.- entinvention-.monntedon the vcasing and in po,- sition for seingv operated by hydraulic pressure.

As illustrated in the drawings, the pressure switch A, in accordancewith the present invention, comprises a housing Il),V which may be cast or otherwise formed .out of a lighi Weight metal, such as aluminum. Thel housing l comprises two principal portions, a substantially circular mounting `Tf1-ange-.l i. .and ..a.solistantially rootansuf.

lar box-like kportion l2 integral with flange and: extendingfroin. oner sidetiieroof. An annue.

lar series: .of holesr L3: are drilledor otherwise provided in thev mounting ilange which are adapted to receive mounting bolts I4 for securine tho-pressure .Switch A at a desired location.

The annular Wail- 1519i thev` mounting flange dellnes an internalpassage L6v therein across which passage transversely extends a cylindrical portion Il. which .is formed-integral with flange Il. Through the cylindrioal portion Il .is lorovided a loneitndinehvextonsiineoore or passage |8 which passagecommunioates with a threaded bore 2 I formed the wallY I5 of theV mounting fion-,ee Il to ropen totneeX-ter-iorat a point furtriest.disposed?fnoinrootaneolar;portion l2. Surrounding the openingvof boss 22 formed integrally with iiange wall |5`and extending therefrom* Adapted to be secured in..

the threadedbore 2| isa cylindrical plug-23 carryf ing exterior threads andhaving-a hexagonal'headf 2dI which facilitates the removal` or insertion of Bore 2| isfoff plugl 23 from orin the-bore 2|. larger diameter than bore I8 with-whichit connects and'is providedwith an annular seat-25 at,` its inner end, againstwhich seatf25-is resteda,v sealing gasket 26; Thegasket 26 is adapted'tobe engaged by a shoulder surfaoeo'f the plug 23- to prevent leakage'oruid therepast.

Sllidahly ttedwithin bore |.8 of cylindricalI portion I1 is alineror sleeve 21 which serves to prevent excess'wear ofthe walls-oflthis bore.

Gasket 26 and plug- 23 act to retain the sleeve 2"|A within its borelrv.

Depending from thebase of the plug 23, integrally formed therewith and adapted to project into the interioroftransverse bore I8 isa. stop or movement limiting cylindrical portion. Carried upon vthe exterior surface ofthe 28. cylindricalv stopZB---and disposed within an. annuvlargroove formed therein is a sealing ring 29.

The stop-281isA engageableby a piston 3| slidably containedvwithin-sleeve 2`| and servesv to limitv the movement of thispiston. Integral with piston 3| andextending-therefrom isan elongatedvpiston rod 32 having itsopposite end projecting through a connecting .opening in flange to extend into the confinesvv of rectangular portion. I2. Piston .3|, `as will be more fully described hereinafter, is adapted to beacted upon by fluid pressure and to bev responsive to variations of such fluid pressure.

Disposed within the piston sleeve or cylinder 2l and slidablymounteduupon pistonrod 32 is a tubular sleeve or spring guide 33 theend 3L of which is adaptedsto be engaged by the piston 3l `where'loy it limits and denes the amount of movement, under fluid pressure,` ,of piston 37|l within cylinder 211i. Spring guide33 atits oppof site end carries an outturned flange vwhich abuts a wasnerformed of; steel or similar ma.-4

terial, which in turn-rests ,upon-a sealing cup3l-` mounted Within aponstricted portion ,3,8y of bore i8. Formed integrally with sealing cup 31 and.

depending from the lbase thereof is a bushing 4l which. closely Iitpswithin opening Y3.0 and ace cepts piston'rodfgigand Serves. to maintainthe pistonv rod: againstglateral- .deiiection and prevents its olores-ing the Surroundingmaterim of fla-nee. Il as it reoinrooates Within opening 30e.

Contained Within sleeve 21 and positioned bore 2| is a cylindrical about the piston rod 32 and a portion of spring guide 33 with one end disposed against the underside of piston SI is a spring 42 which is of comparatively light construction and which is adapted to eXert its bias to maintain piston 3I in contact with stop 28. The opposite end of spring 42 is seated upon one end of a more massive spring 43 which surrounds spring guide 33 and is considerably heavier in construction than spring 42. The other end of spring 43 is seated upon the circular flange 35 provided by spring guide 33. Before heavier spring 43 can be compressed piston 3i must move to compress lighter spring 42 upon its seat on heavy spring 43 in a manner and for a purpose which will be later described when the operation of pressure switch A is outlined below.

Housed within sealing cup 31 and adapted to be retained therein by washer 36 which closes cup 31 is a group of chevron-shaped seals 44 which are designed to prevent fluid from flowing along piston rod 32 into the interior of rectangular portion I2.

Fluid for effecting movement of the piston 3I enters the bore I8, as best shown in Figure 2, through an orice 45 formed in the underside of cylindrical portion I1, which orifice 45 communicates with an annular groove 46 in sleeve 21. A plurality of openings 41 lead from the annular groove 46 to within the interior of sleeve 21; thus the fluid which enters through orifice 45 will flow around groove 46 and through openings 41 into the sleeve 21. A transverse opening 48 through stop 28 provides a passage for this fluid which then flows through a longitudinal bore I in stop 28 to impinge upon the piston 3| to move it.

When fluid under pressure is fed into cylinder bore I8 there is a possibility that a certain amount will leak past the piston 3I to the spring side thereof. To prevent such fluid from collecting in bore I8 there is provided a bleed or draining hole 52 formed in the wall I5 of the mounting flange I I adjacent sealing cup 31 and leading to the exterior of the housing. Thus the possibility that suicient fluid could accumulate in cylinder bore I8 to hamper the movement of piston 3l, or to be forced past chevron seals 44 into rectangular portion I2 is obviated. Since the by-passed fluid must first reach drain hole 52 before it can be scaveneged therethrough, the washer 36 is provided with a number of openings (not shown) which permit the passage of iluid for flow to drain hole 52.

Rectangular portion I2 of housing I0 comprises a base 53, three upstanding walls 54, 55, and 56, with the fourth or closing Wall being provided by the mounting flange II. These several walls cooperate to define a cavity or switch chamber 51 into which the end of piston rod 32 projects. A cover 58 closes switch chamber 51, being secured to rectangular portion I2 by suitable studs 59. Securely mounted as by means of studs 6B, or similar fasteners, upon the projecting end of piston rod 32 is a generally L-shaped block or carriage 6I having a slotted leg 62, which carriage 6I is adapted to be longitudinally displaced, relative to rectangular portion I2 by movement of piston rod 32. Pivotally mounted Within the slot of leg 62 and toward the forward end thereof, as by a pin 63, i-s a trigger 64. Trigger 64 is biased into an upright position by a spring 65 which is housed within a longitudinally extending cylindrical hole 66 formed in leg 62. One end of Spring 65 seats against the base of hole 66 and Cil the other rests against the trigger 64. Trigger 64 comprises an upright, vertical switch actuating arm 61 having a radiused top portion 6G which is adapted to actuate a switch, as will be hereinafter described. Adjacent the arm 61 and spaced from the top 68 thereof is a stop portion 1I which is adapted to engage an end surface 12 on leg 62 of carriage 6I at the forward end thereof to prevent the forward declination of vertical arm 61 of trigger 64 for a reason to be described below. Secured to the wall 56, as by bolt and nut assemblies 13, is a guide block 14 which is slidably engageable by leg 62 of carriage 6I and maintains the carriage and the trigger 64, which it carries, in the desired path of movement and further prevents distortion or misalignment of the carriage 6I upon its support on rod 42 when pressure is applied to trigger 64.

Mounted within the confines of switch chamber 51 and secured to base 53 is a usual selfcontained snap switch 15, of the micro-switch type, having the usual stationary contact and resilient Contact arm carrying a movable contact, with the latter being biased normally to contacts disengaged position and with an outwardly biased actuating switch button 16 protruding from the interior of the casing 11 of switch 15 and extending into the path of trigger 64 whereby it may be engaged and depressed on movement of the trigger to move into the switch casing 11 to actuate the movable contact therein into contacts engaged position. It is understood that the particular construction of switch 15 has no bearing on the present invention and the invention is not limited to the type illustrated as any circuit controlling instrumentality, or" suitable size, adapted to be actuated by movement of the trigger 64 to eifect an electrical operation may be used.

Switch 15 is secured to base 53 and a shield member 18 is disposed upon switch 15 by a pair of mounting bolt and nut assemblies 19. Conducting leads 8I run from switch 15 into a usual electric connecting plug 82 which is secured to an annular boss 83 formed on wall 54 of switch box I2.

The pressure switch A of the present invention is adapted for use in any system wherein it is desired that on variation of an external pressure from normal an electric circuit controlling instrumentality is actuated to perform a desired operation. One use of the present pressure switch is disclosed and fully described in a co-pending application, Serial No. 778,933, led October' 9, 1947. In this co-pending application the pressure switch A is applied to a conventional torque nose carrying aircraft engine B, a fragmentary portion of which is illustrated in Figure 4, being mounted upon the nose casing 84 thereof. The Vertical sectional view of Figure 4 illustrates the manner of mounting of switch A to the aircraft engines nose casing 84. As shown switch A is secured to nose casing 84 by a plurality of mounting studs I4 and located over a bore or channel 86 in the casing. A plate 88 ts completely over the top surface of mounting flange II of switch A to seal off the passage I6 therein and is held thereon by the studs I4. Fluid such as oil lls the bore 86 in nose casing 84 and passage I6 in mounting flange I I and completely surrounds the cylindrical portion I1. As the engine B, with which pressure switch A in this example is associated, is started up, oil under pressure is directed through channel 86 in nose casing 84 to pressure switch A. This oil flows through hole 45 in the wall yof` kcylindrical' portion; -|1, about annular groove 469in sleeve 2.1y and through the holes 41 into the interior of^l sleeve 21y disposed inbore I8.. As theenginepower'output is` increased piston 3| moves, under thepressure developed, along bore Hyland; againstV the force of. thel light spring 42 to compressthelatter, and'when normal engine powerv output is attained the oil pressure developed will` have additionally compressed.r heavy spring 43. The movementy of the piston 3| under thedevelopedpressure causes simultaneous movementrof: the'piston rod 32 and displaces the carriage; 6| and its associated trigger64, to the right, as. viewed in'Figure'Z, to thedotted .line position thereinzillustrated. Itisherenoted that trigger 64ras. itmoves past the switch'button 16 does not actuate'it into -switch casing. 11 to causethe operationloftswitchl but ratheritself is actuated-and pivots, on contact with` button 16in a counterclockwise directionagainst the bias'of its spring 65 to travel past button 16 without moving it. Immediately lafter it has cleared button 16, spring returnstrigger 64 toits upright position. The positionV occupied bythe-trigger 64 at the right of switch button 16 isfits armed position and is attained only when the'engine B is developing a predetermined;v number of pounds of torque, Shouldfgreater. torque-be, developed by the engine there vlwill be a tendency for the piston 3| to be driveny further to the right against the bias of spring 43-.but the amountof its travel in this direction is limited by the end 34 of spring guide 33 which will be-engagedby the piston 3|.

The two springs 42 and 43 are provided to per-v mit theVv gradual movement ofV piston 3| and carriage 6| to armed position which position the. springs determine will be reached only on attainment by the engine of a predetermined torque pressure. Since it would-be extremely diiiicult to provide a single spring having the compound characteristics of initial light resistance to the movement of piston31| and subsequent stiff resistance when a predeterminedpoint is reached the two springs 42 and 43 have beenprovided. The predetermined-torque pressure lat which the pressure switch A isarmed: is determined by the minimum effective-power output of the engine B.- When the torque, pressure developed by engine. B falls below thepressure required to compress light spring 42 and tobegin the compression of heavy spring 43, the lessenedvpressure appliedto piston, 3| permits it to be pushed sharply and quickly to the left under the force of expanding heavy spring 43. The initial impetus to effect movement of .carriage 6| and its associated trigger 64is given by the 'heavyI spring 43 and a quick responsey to a drop in' applied pressure is thus achieved. As trigger 64 strikesswitch button 'i6 it depresses-it into its casing 11 to close the normally open contacts of switch 15 and complete a circuit to effect an electrical operation desired. Spring 43 exhaustsits travel path at this moment and light spring 42 takes over to continue to move piston 3| to the limit of its travel to the left. Since the power of-spring 42v is less than that of spring 43 the movement of piston 3|, piston rod 32 and the carriage 6| mounted thereon is slowed and `therefore the period of time in which the-trigger 64 remainsin contact with and holdsy switch button 16 depressed is prolonged to assure that the normally opened contacts of switch '|51do-close, .Declination to the-right or clockwise movement ofthe trigger 64 as itengages switch` button 16, in thisoperation, is prevented by theengagement of stop 1| of trigger 64 with 6? the stop seat12iprovided by.` leg 62'0fj carriage -'6|. Spring 42 will bringipiston,3|fto;rest1 against stop, 28vprovided by plug 23,2 when: engine B ceases-to deliver power.

The pressure'switch A ofthe presentinvention has beenv described in association with. any engine whose power output: determines the'timezoffoperation. of the switch. It is understood and-contemplated as within thescopeof this invention that the switch A can be utilized in any fluid system wherein variations, in Apressure will be encountered and desired operations will occur 'at predetermined pressure conditions.

While certain preferred embodiments of the inventionv have been specificallyr disclosed, it is understood that the invention; is` not limited thereto as manyvariations will be readily apparent to those skilled-in` the artV andl the invention is tobe given its broadestpossible interpretation within the terms ofthe following claims.

I claim:

1. In a pressure switch, a housing comprising wall portions dening a chamber, an electric circuit controlling instrumentality mounted in said chamber, an actuating member'movable. to operate said electric circuit controlling instru:- mentality, and a pressure responsive means for moving said actuating member, said pressure responsive means comprising'ay rectilinearly mov-v able member, apivotalmember supported thereon, a stop means engageableby said, pivotal member, said pivotal member being bodily movable, by and uponV movement of saidfrectilinearly movable member, into engagement with said instrumentality actuating member tof-be pivotedthereby in one direction untilmovedy therepast, and means to move said pivotal member-in theopposite direction to occupy a triggering position, from which position on returnmovement'of said rectilinearly movable member-said pivotal member engages and'moves said actuating. member'to operate said electricr circuit controlling instrumentality, said stop means, in this latter-movement, restraining said pivotal member against pivotal movement.

2. In a pressure switch, a housing comprising wall portions defining a chamber,- an electric circuit controlling instrumentality mounted in said chamber, an actuating member movable to operate said electric circuit controlling instrumentality, and a pressure responsivemeans for moving said actuating member, said pressure responsive means comprisinga rectilinearly movable member, a pivotal-member'suppor-ted` there,- on, a stop means engageableby saidv pivotal member, spring means exerting its bias upon said pivotal member for engagement of said pivotal member with said stop means, said pivotal member being bodily movable, by and upon movement of said rectilinearly movable member, into engagement with said instrumentality actuating member to be pivoted thereby, against the bias of said spring means, until moved therepast to occupy a triggering position, from which position on return movement of said rectilinearly movable member said pivotal member engages and moves said actuating member Yto operate said electric circuit controlling instrumentality, said stop means, in this latter-movement, restraining said pivotal member-against pivotal movement.

3. In a pressure switch, ahousing comprising wall portions defining a chamber, anV electric circuit controlling instrumentality,v mounted in said chamber, an actuatingmember-rectilinearly movable to operate said electriccircuit controlling instrumentality, and a pressure responsive means for moving said actuating member, said pressure responsive means comprising a rectilinearly movable member, a support member carried thereby, a pivoted member mounted on said support member, stop means provided by said support member engageable by said pivoted member, spring means contained within a recess in said support member and bearing upon said pivoted member to bias it toward engagement with said stop means, said pivoted member being bodily movable, by and upon movement of said rectilinearly movable member, into engagement with said instrumentality actuating member to be pivoted thereby, against the bias of said spring means, until moved therepast to occupy a triggering position, from which position on return movement of said rectilinearly movable member said pivoted member engages and moves said actuating member rectilinearly to operate said electric circuit controlling instrumentality, said stop means, in this latter movement, restraining said pivoted member against pivotal movement.

4. In a pressure switch, a housing comprising wall portions dening a chamber, an electric circuit controlling instrumentality mounted in said chamber, an actuating member movable to operate said electric circuit controlling instrumentality, and a pressure responsive means for moving said actuating member, said pressure responsive means comprising a member rectilinearly movable in response to fluid pressure acting thereupon, spring means exerting its bias on said movable member to oppose said movement, a pivotal member supported thereon, a stop means engageable by said pivotal member, spring means biased against said pivotal member and urging it into engagement with said stop means, said pivotal member being bodily movable, by and upon movement of said rectilinearly movable member, into engagement with said instrumentality actuating member to be pivoted thereby, against the bias of said second-mentioned spring means, until moved therepast to occupy a triggering position, from which position on return movement of said rectilinearly movable member said pivotal member engages and moves said actuating member to operate said electric circuit controlling instrumentality, said stop means, in this latter movement, restraining said pivotal member against pivotal movement.

5. In a pressure switch, a housing comprising wall portions defining a chamber, an electric circuit controlling instrumentality mounted in said chamber, and a pressure responsive means for effecting the operation of said instrumentality, said pressure responsive means comprising a member rectilinearly movable in response to uid pressure acting thereupon and having a portion thereof disposed within said chamber, a pair of spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to urge said member outwardly of said chamber, one of said spring means being compressible by the other upon movement of the rectilinearly movable member, a member pivotally mounted on said rectilinearly movable member on the portion thereof disposed within said chamber and bodily movable therewith to operate said electric circuit controlling instrumentality, stop means engageable by said pivoted member to restrain movement thereof in one direction, and resilient means exerting its bias normally to maintain said pivoted member in engagement With said stop means.

6. In a pressure switch, a housing comprising Wall portions defining a chamber, an electric circuit controlling instrumentality mounted in said said chamber, an actuating member rectilinearly movable to operate said electric circuit controlling instrumentality, and a pressure responsive means for moving said actuating member, said pressure responsive means comprising a rectilinearly movable member having a portion thereof disposed within said chamber, a pair of spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to urge said member outwardly of said chamber, one oi said spring means being compressible by the other upon movement of the rectilinearly movable member in response to uid pressure acting thereupon, a support member carried by second mentioned rectilinearly movable member on the portion thereof within said chamber, a pivoted member mounted on said support member, stop means provided by said support member engageable by said pivotal member, spring means contained within a recess in said support member and bearing upon said pivoted member to bias it toward engagement with said stop means, said pivoted member being bodily movable, by and upon movement of said rectilinearly movable member, into engagement with said instrumentality actuating member to be pivoted thereby, against the bias of said spring means, until moved therepast to occupy a triggering position, from which position on return movement of said rectilinearly movable member said pivoted member engages and moves said actuating member rectilinearly to operate said electric circuit controlling instrumentality, said stop means, in this latter movement, restraining said pivoted member against pivotal movement.

7. In a pressure switch, a housing comprising a substantially rectangular portion provided with a chamber, and a substantially circular mounting portion, said circular mounting portion providing a support for a rectilinearly movable pressure responsive member a portion of which extends into said chamber, said circular portion having openings therein whereby fluid under pressure may be applied to said rectilinearly movable member for effecting movement thereof into said chamber, spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to oppose movement of said member into said chamber, an electric circuit controlling instrumentality mounted in said chamber, and a member movably mounted upon the portion of said rectilinearly movable member disposed within the chamber and being bodily movable with said rectilinearly movable member to operate said electric circuit controlling instrumentality.

8. In a pressure switch, a housing comprising a substantially rectangular portion provided with a chamber, and a substantially circular mounting portion, said circular mounting portion providing a support for a rectilinearly movable pressure responsive member a portion of which extends into said chamber, said circular portion having openings therein whereby iiuid under pressure may be applied to said rectilinearly movable member for eiecting movement thereof into said chamber, spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to oppose movement of said member into said chamber, an electric circuit controlling instrumentality mounted in said chamber, a member pivotally aannam -mounted upon the yportion *of* saidrectllinearly movable member disposed within Ythe chamber and being bodily movable "with said rectilinearly movable member to operate said electric circuit controlling instrumentality, stop means engagerable by said pivoted member to restrain moveeffecting movement thereof into said chamber,

spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to oppose movement of said member into said chamber, an electric circuit controlling instrumentality mounted in said chamber, an

actuating member operatively associated with said electric circuit controlling instrumentality and movable to operate said instrumentality, a pivotal member mounted upon the portion of said rectilinearly movable member disposed within the chamber, a stop means engageable by said pivotal member, spring means urging said pivotal member into engagement with said stop means, said pivotal member being bodily movable, by and upon movement of said rectilinearly movable member, into engagement with said actuating member to be pivoted thereby, against the bias of said spring means, until moved therepast to occupy a triggering position, from which position on return movement of said rectilinearly movable member said pivotal member engages and moves said actuating member to operate said electric circuit controlling instrumentality, said stop means, in this latter movement, restraining said pivotal member against pivotal movement.

10. In a pressure switch, a housing comprising a substantially rectangular portion provided with a chamber, and a substantially circular mounting portion, said circular mounting portion providing a support for a rectilinearly movable pressure remonsive member a portion of which extends into said chamber, said circular portion having openings therein whereby fluid under pressure may be applied to said rectilinearly movable member for effecting movement thereof into said chamber, a pair oi spring means disposed upon said rectilinearly movable member exteriorly of said chamber and operative to oppose movement of said member into said chamber, one of said spring means being compressible by the other upon movement of the rectilinearly movable member, an electric circuit controlling instrumentality mounted in said chamber, an actuating member operatively associated with said electric circuit controlling instrumentality and rectilinearly movable to operate said instrumentality, a pivotal member mounted upon the portion of said rectilinearly movable member disposed within the chamber, a stop means engageable by said pivotal member, spring means urging said pivotal member into engagement with said stop means, said pivotal member being bodily movable, by and upon movement of said rectilinearly movable member into engagement with said actuating member to be pivoted thereby,

10 against-the bias'ofy said "spring'means, until moved therepast to occupy a triggering position, from which position-on return movement of said rectilinearly movable member lsaid pivotal member engages and imoves `saidactuatingl member to operate said-electricfcircuit controlling instrumentality, said stop means, in'this llatter movement,

`restraining saidfpivotal member against pivotal movement.

11. In a'pressure switch, a housingcomprising Asaid circular mounting -portion and lextending from one side-thereof, said |rectangular portion having a chamber formed therein, said circular mounting portion comprising an annular wall defining a central passage and a cylindrical portion integral with said annular wall and extending transversely across said passage, said cylindrical portion provided with a longitudinally extending bore which opens into the chamber in said rectangular portion, an electric circuit controlling instrumentality mounted in said chamber in said rectangular portion, and an actuating means for effecting the operation of said instrumentality, said actuating means comprising a pressure responsive member slidably disposed in said longitudinally extending bore and having an end extending into said chamber, and means carried by said end and bodily movable therewith to operate said electric circuit controlling instrumentality.

12. In a pressure switch, a housing comprising a substantially circular mounting portion and a substantially rectangular portion integral with said circular mounting portion and extending from one side thereof, said rectangular portion having a chamber formed therein, said circular mounting portion comprising an annular wall defining a central passage and a cylindrical portion integral with saidannular wall and extending transversely across said passage, said cylindrical portion provided with a longitudinally extending bore which opens into the chamber in said rectangular portion, an electric circuit controlling instrumentality mounted in said chamber, and a pressure responsive means for effecting the operation of said instrumentality, said pressure responsive means comprising an elongated member slidably disposed within said longitudinally extending bore for rectilinear movement in response to fluid pressure acting thereupon, and having an end thereof extending into said chamber in said rectangular portion, spring means disposed in said longitudinally extending bore exerting its bias to oppose movement of said elongated member, and means provided on said extending end of said elongated member and bodily movable therewith to operate said electric circuit controlling instrumentality.

13. In a pressure switch, a housing comprising a substantially circular mounting portion and a substantially rectangular portion integral with said circular mounting portion and extending from one side thereof, said rectangular portion having a chamber formed therein, said circular mounting portion comprising an annular wall defining a central passage and a cylindrical portion integral with said annular wall and extending transversely across said passage, said cylindrical portion provided with a longitudinally extending bore which opens into the chamber in said rectangular portion, an electric circuit controlling instrumentality mounted in said chamber, and a pressure responsive means for electing the operation of said instrumentality, said pressure responsive means comprising an elongated member slidably disposed Within said longitudinally extending bore for rectilinear movement in re spouse to fluid pressure acting thereupon and having an end thereof extending into said chamber in said rectangular portion, a pair of spring means disposed in said longitudinally extending bore and operative upon said elongated member to resist movement thereof into said chamber, one of said spring means being compressible by the other upon movement of the elongated member, and means supported on said extending end of said elongated member for movement there- The following references are of record in the le of this patent:

UNITED STATES PATENTS 10 Number Name Date 775,665 Scott NOV. 22, 1904 1,257,694: Gadke Feb. 26, 1918 2,261,714: Canneld NOV. 4, 194.1 

